The invention relates to an inclination adjustment lock for seat backs.
In a known inclination adjustment lock of the type disclosed in DE 198 59 239 C1, a first lock part is firmly attached to a first partial area, and a second lock part is attached to a second partial area. The second lock part is mounted on an axis parallel to the pivot axis for the first partial area, and is held in a ratcheting position by means of a locking pawl, in which the second lock part engages by means of an opposing toothed area of the first lock part.
An intermediary toothed area is provided on the second lock part of the known inclination adjustment lock that is engaged with a first toothed area of an intermediary element. The intermediary element may be engaged and disengaged via a second toothed area finer than the first toothed area with a corresponding opposing toothed area of the first lock part. The intermediary element is mounted on a second lock part so that it may be moved to a limited extent perpendicular to the pivot direction and tangential to the first toothed area.
Provision of an intermediary element, i.e., provision of an additional component, is expensive. This expense is further increased by the fact that this intermediary element must be mounted on the second lock part so that it may move longitudinally in a certain manner. The expense caused by the known inclination adjustment lock was previously necessary to ensure that slippage of the engaged toothed areas is prevented even during high loads caused by crashes. A better attachment must thus be provided for the known inclination adjustment lock when a tangential displacement of the engaged toothed areas arises during a crash, and also when the corresponding deformation is no longer elastic, but rather plastic.
Inclination adjustment locks of the same type are known in which the first lock part is formed of a toothed segment rigidly attached to the seat back as in DE 197 09 524 A1. In this solution, the second lock part is a pivoting ratchet pawl whose toothed area may be pivoted to engage and disengage with the toothed part of the toothed segment. The ratchet pawl is held in the engaged position by a locking pawl that also pivots. In this known solution, the ratchet pawl is provided with a constricted area of lesser width between its pivot axis and the contact area of the locking pawl opposite the toothed area. In the known solution, this constriction serves to maintain the locked position between the interacting toothed areas during an elastic deformation such as may occur during pulsed loads. In the known solution, the teeth of the toothed areas held engaged are symmetrical, and have the same shape. In such toothed areas, the problem arises that, during a crash, the toothed area is not loaded equally, but rather the first tooth adjoining the load application point breaks off, as may a part of the second tooth. The remaining toothed area may then slip.
Based on the state of technology described above, the invention has the task of creating an inclination adjustment lock of the type described in the overall concept as simply as possible and from as few components as possible, and to make it so safe during increased loading situations, such as during a crash, that the engaged toothed areas are loaded equally, and that they remain engaged during the crash.
The present invention features An inclination adjustment lock for seat backs including a first lock part and a second lock part, one of which is firmly attached to a first seat back partial area and the other of which is attached to a second partial area of the seat back, whereby both partial seat back areas are connected together so that they may pivot about a common pivot axis. The second lock part (4) is mounted to the second partial seat back area (9b) so that it may pivot about an axis (4a) parallel to the pivot axis (3) and so that it may be held via a locking pawl (5) in a ratchet position in which a toothed section (4b) of the second lock part (4) engages with an opposing toothed section (2a) of the first lock part (2).
Utilizing the present invention. The pressure angles (xcex1, xcex3) of the tooth faces receiving increased loading conditions that are greater than at rest loading conditions, decrease to the toothed section (4b) of the second lock part (4) and on a complementary opposing toothed section (2a) as the separation from the axis (4a) increases.
In accordance with another feature of the present invention, the inclination adjustment lock includes tooth faces wherein each different tooth face of a tooth (2c; 2d; 2e and 4c; 4d; 4e; 4f) or of a corresponding tooth gap (4g; 4h; 4i and 2f; 2g; 2h; 2i) has a different pressure angle value (xcex1, xcex2 or xcex3, xcex4) during at rest load conditions and wherein unloaded faces all have the same pressure angle (xcex2 or xcex4) during increased loading conditions.
In one embodiment, there is a central plane between the faces of each tooth (2c, 2d, 2d, 2e), and wherein the central planes between the faces of each tooth (2c; 2d; 2e) intersect at a central point. In yet another embodiment, a thickness (d) of teeth adjacent to the tooth bases (2c; 2d; 2e or 4c; 4d; 4e; 4f) decreases as the separation from axis 4a increases.
The recommended solution takes into account the unequal loading situation of the teeth located at differing distances from the point where force is applied. Such a solution as provided by the present invention allows for an even distribution of the load to all engaged tooth faces that, with known prior art solutions, are borne by only one or two teeth during an increased load condition, such as during a crash.